Mike Roberts

Researchers Identify Second Citrus Canker Gene

A team of UF/IFAS researchers has identified a second citrus canker gene that could potentially lead to citrus cultivars that are resistant to the disease and other pathogens, as well. Citrus canker is a bacterial disease that reduces the vitality of citrus trees and renders the fruit unmarketable. Once considered eradicated in Florida, citrus canker reared its ugly head again in 1995. Eradication efforts were undertaken, but a series of hurricanes spread the pathogen across the state, and Florida citrus growers have been battling it ever since. The disease has since spread to Louisiana, Texas, and other states. However, hope may be on the horizon. A team of researchers with the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) have identified a second citrus canker gene; these are genes that control a plant’s negative reactions to a pathogen. This could allow researchers to target the new gene using gene editing to create citrus cultivars that are resistant to citrus canker and possibly other pathogens. 

Citrus Canker Gene Details
According to UF/IFAS, gene editing can “knock out” those genes in a plant that make it susceptible to diseases. The team of UF/IFAS researchers, including Zhanao Deng and Fred Gmitter, identified the citrus canker gene—CsDMR6—which affects a citrus tree’s reaction to the pathogen that causes citrus canker. CsDMR6 is the second gene identified that, when working normally, would inhibit a citrus plant’s ability to defend itself from citrus canker.

Researchers will now be able to attempt to edit the CsDMR6 gene in new cultivars so that the gene is not activated in the plants when citrus canker infection starts. In this way, the new citrus tree cultivars are resistant to the pathogen because the undesirable symptoms caused by the gene never begin. 

CsDMR6 is the second gene found responsible for a citrus plant’s reaction to citrus canker. The first was the citrus gene LOB1, identified by UF/IFAS professor of microbiology, Nian Wang. According to Zhanao Deng, a UF/IFAS professor of environmental horticulture and one of the UF/IFAS team members, having another gene to edit will give researchers a better chance to create canker-resistant citrus.According to the research, plants like grapefruit and Carrizo, or giant cane, that had their CsDMR6 gene “knocked out” showed resistance to citrus canker, expressed plant defense genes at higher levels and contained more salicylic acid. Similarly, editing CsDMR6 in other plants led to a broad resistance to other pathogens, such as different species of bacterial pathogens. Researchers are hoping that the discovery of CsDMR6 could also play a role in creating citrus resistant to Huanglongbing (HLB), or citrus greening.

This column is sponsored by Griffin Fertilizer Co., and the opinions expressed herein may not reflect those of CFAN or of its advertisers.  

BIO: Mike Roberts is the Vice President of the Frostproof, Fla.-based Griffin Fertilizer Co. Roberts joined the company in November 2011. He has spent the majority of his career in the fertilizer/agchem industry. Roberts earned a Bachelor of Science degree in citrus production from Florida Southern College in Lakeland. For more information, visit griffinfertilizer.com.

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